Scottish first minister, Alex Salmond, is said to be considering legal action over his exclusion from the mooted TV leadership debates, which, with theoretical agreement from the three main parties, may soon cease to be the media pipe-dream they have been here since a generation of young TV executives watched Jack Kennedy knock out Richard Nixon in 1960.

I think Salmond's lawyers would be howling at the moon – he can claim no more than his own debate, on Scottish television, with the rivals for his position – and I want to go even further: not only should Salmond be denied a lectern, but so should Nick Clegg.

There are both political and artistic reasons for this veto. In democratic terms, such a stand-off should be a fight for the keys to No 10, just as the American game-show offers the prize of use of the White House bowling alley. There is no possibility the Lib Dem will become premier, so he has as much place in a prime ministerial debate as in a US presidential one.

It's true that Clegg might get to be kingmaker in a hung parliament, so he might be admitted to one of the three planned debates to address the issue of which way he might swing; the other two should feature just the other two.

The case for a Labour-Conservative debate is also supported by television grammar. The American debates – on which any British version would inevitably be modelled – reflect a two-party system. The biggest exception was 1992, when a third candidate, Texan oilman Ross Perot (pictured), literally stood bet- ween George HW Bush and Bill Clinton.

The effect was dramatic or, rather, anti-dramatic: Perot, who had a history of hostility to Bush, joined with the Democrat against the incumbent Republican, so that Clinton's footwork was never tested in the way that, for good or ill, Kennedy's, Dukakis's and later Obama's were.

Cameron v Brown is the bout most viewers want to see. A leadership debate is political boxing, and the rules of that sport were carefully drawn never to have three people in play.